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- Pettersson, Jesper, 1978, et al.
(författare)
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A pilot plant study of the effect of alkali salts on initial stages of the high temperature corrosion of alloy 304L
- 2004
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 461-464, s. 965-972
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Tidskriftsartikel (refereegranskat)abstract
- Alloy 304L was exposed for between 15 min to 12 hr in the 12MW CFB research boiler at the Chalmers university of technology using an air-cooled probe. The base fuel consisted of a mixture of 67% wood chips and 33% pellets. In addition to the base fuel experiment, a number of exposures were performed where S and Cl was added to the fuel in the form Of SO2(g) and HCl(aq) in order to control the flue gas chemistry in the superheater region. After the exposures the samples were analysed by ESEM/EDX, XRD and SAM. Burning a mixture of woodchips/pellets without adding sulphur or chlorine results in the formation of K2SO4 deposits on the corrosion probes. When HCl is added to the fuel KCl deposits form. The simultaneous addition of HCl and SO, results in a deposit consisting of a mixture of KCl and K2SO4. In all environments studied an oxide in the 100nm range forms. With time, the oxide becomes covered by ash deposits. After exposure to the biomass flue gas environment, the oxide is enriched in K, especially the outer part. Chlorine is not present in the oxide even when the KCl(s) forms on the surface. It is suggested that potassium chromate formation occurs by the reaction of potassium chloride with chromium oxide.
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| 2. |
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| 3. |
- Sasaki, S, et al.
(författare)
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Dexterous finger movements in primate without monosynaptic corticomotoneuronal excitation
- 2004
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Ingår i: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 92:5, s. 3142-3147
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Tidskriftsartikel (refereegranskat)abstract
- It is generally accepted that the precision grip and independent finger movements (IFMs) in monkey and man are controlled by the direct (monosynaptic) corticomotoneuronal (CM) pathway. This view is based on previous observations that pyramidotomy causes near permanent deficits of IFMs. However, in addition to the direct CM pathway, pyramidotomy interrupts several corticofugal connections to the brain stem and upper cervical segments. Indirect (oligosynaptic) CM pathways, which are phylogenetically older, have been considered to be of little or no importance in prehension. In three adult macaque monkeys, complete transection of the direct CM pathway was made in C4/C5, which is rostral to the forelimb segments (C6–Th1). Electrophysiological recordings revealed lack of the direct lateral corticospinal tract (LCST) volley, monosynaptic extracellular field potentials in the motor nuclei, and monosynaptic CM excitation. However, a disynaptic volley, disynaptic field potentials and disynaptic CM excitation mediated via C3–C4 propriospinal neurons remained after the lesion. Thus the lesion interrupted the monosynaptic CM pathway and oligosynaptic LCST pathways mediated by interneurons in the forelimb segments. Precision grip and IFMs were observed already after 1–28 days postoperatively. Weakness in force and deficits in preshaping remained for an observation period of 3 mo. Indirect CM pathways may be important for neuro-rehabilitation.
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| 4. |
- Segerdahl, Karin, 1974, et al.
(författare)
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Is KCl(g) corrosive at temperatures above its dew point? - Influence of KCl(g) on initial stages of the high temperature corrosion of 11% Cr steel at 600 degrees C
- 2004
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Ingår i: High Temperature Corrosion and Protection of Materials 6, Prt 1 and 2, Proceedings. ; 461-464, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- The influence of gaseous KCl on the high temperature oxidation of CrMoV11 1 (X20) steel at 600degreesC is reported. The sample temperature was above the dew point of KCl, the partial pressure of KCl being about 5ppm. The samples were investigated by a number of surface analytical techniques including grazing angle XRD, SEM/EDX, and SAM. CrMoV11 1 steel shows protective behaviour in clean dry O-2 and O-2/H2O environment because of the formation of a chromium-rich oxide (alpha-(Fe,Cr)(2)O-3). It is Often considered that alkali salts accelerate the corrosion of steel only when present on the surface in solid or liquid form. In contrast, the present result shows that gaseous KCl is very corrosive, also in the absence of condensation. KCl(g) reacts with chromium in the scale, forming K2CrO4(s). This depletes the protective oxide in chromium and leads to the formation of non-protective hematite, Fe2O3.
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